variables

[Jules]

Quickie from a newbie
How do I change the value of a variable, say var, of ClassA from a different
class, say ClassB?
TIA
Remove XX if replying direct

[Ryan Stewart]

"Jules" <[e-mail]> wrote in message
news:bj**********@newsg3.svr.pol.co.uk...

Quickie from a newbie
How do I change the value of a variable, say var, of ClassA from a different class, say ClassB?
TIA
Remove XX if replying direct

If I understand your question, you don't unless var's type is some
super-class of both ClassA and ClassB. If this is what you want to do:

ClassA var;
var = new ClassA();
// Do something with var
var = new ClassB();

That doesn't work. It's like saying:

int x = "Hello world.";

Some languages would call it a type mismatch. You could, however, say:

Object var;
var = new ClassA();
// Do something with var
var = new ClassB();

[Brad BARCLAY]

Jules wrote:

Quickie from a newbie
How do I change the value of a variable, say var, of ClassA from a different
class, say ClassB?

Quick question, but a long, convoluted answer :).

The answer is "it depends". There are three factors that need to be
dealt with:

1) Is the variable a static (or class) variable, or is it an instance
(object) variable?

2) What is the variable's visibility?

3) Are ClassA and ClassB in the same package?

(There are potentially more than three if you're working in a
multithreaded environment, but as you said you're a newbie, I'll presume
not).

Look up "member visibility" in any convienent Java programming
reference. You first need to be certain that ClassB has the necessary
rights to modify a field (variable) in ClassA in the first place.

Once you've assured yourself that you have such rights, how you'll do
the assignment depends on wether or not the variable is static.

If the variable is static, use:

ClassA.var = somevalue;

If the variable is non-static, use:

instanceOfClassA.var = somevalue;

...where "instanceOfClassA" is a field that was generated by creating a
"new" instance of ClassA, ie:

ClassA instanceOfClassA = new ClassA();

HTH!

Brad BARCLAY

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